The underwater magnetotelluric method is a technique performed on the water surface with the utilization of distant reference. Combined with the authors' practical experience, the present paper has described the working method of underwater magnetotelluric sounding technique (MT method) used in such waters as lakes and swamps as well as the measures taken for obtaining high-quality sounding data, and summed up some experience and understanding acquired in the work. All this provides basis for carrying out MT work in large area of waters.